1. Field of the Invention
This invention relates to a method for controlling the rotational frequency of a weaving machine and an apparatus therefor and, more particularly, to a method for controlling the rotational frequency of a weaving machine so as to increase the quantity of production and an apparatus therefor.
2. Description of the Prior Art
In a weaving machine, the rotational frequency to maximize the quantity of production depends upon not only the kind of weaving machine and resultant woven fabric, but also upon the skill of an operator and the tolerance limit of the quality of woven fabric or the like. Thus, in the weaving machine, there is a case where the quantity of production is reduced by increasing the rotational frequency while there is another case where the quantity of production is increased by reducing the rotational frequency.
The above cases take place for the reason that since end breakage of warp and unsatisfactory weft insertion are liable to occur by increasing the rotational frequency, the number of times of stop, or the stop frequency, of the weaving machine caused by the end breakage of warp and unsatisfactory weft insertion is increased. When the stop frequency of the weaving machine is increased, the working allowance of the operator and the operating rate of the weaving machine are reduced, thus resulting in the further reduction in quantity of production than before the rotational frequency is increased, and besides, the degradation in quality of woven fabric occurs.
As one of weaving machine control methods which permit the quantity of production to increase by controlling the rotational frequency of a weaving machine, Japanese Patent Public Disclosure (KOKAI) No. 61-239057 (U.S. Pat. No. 4,736,324, EP-A-0182382) has disclosed a method of increasing the rotational frequency of a weaving machine when an allowance is made for the operating rate of the weaving machine.
According to this conventional control method, however, since the rotational frequency is determined on the basis of the operating rate resulting from varying the rotational frequency, the weaving machine is subjected to repetition of a series of steps, i.e., the increase in the operating rate, the increase of the rotational frequency, the increase in the stop frequency, the reduction in the operating rate, the reduction in the rotational frequency, the reduction in the stop frequency, the increase in the operating rate and the increase in the rotational frequency, for example. Therefore, in the conventional control method, the rotational frequency should be temporarily reduced, so that the increase in the final quantity of production is small.